1. Field of the Invention
The present invention relates to a molded elastomer for an endoscope.
2. Description of the Related Art
In endoscopes, a molded elastomer containing a fluorine-containing elastomer with excellent chemical resistance is used as an outer cover for a curved tube used therein. Such a molded elastomer may be, for example, a rubber tube for a curving section, which is molded by cross-linking a kneaded mixture containing prescribed starting materials. The starting materials used may include, for example, a ternary copolymer of vinylidene fluoride/hexafluoropropylene/tetrafluoroethylene, a liquid fluorine-containing elastomer, perhexa 2,5B, triallyl isocyanate, hydrated silica, and reinforcing carbon.
It is required to be completely disinfected and sterilized for medical endoscopes, and recently a new disinfecting and sterilizing method has come into use. According to the method, chemical liquid which turns into water or harmless substance after the treatment, i.e., which is non-polluting and gives no environmental destruction is used. Specifically, hydrogen peroxide plasma, peracetic acid, acidic water, or the like is used. An autoclave method which is performed under high temperatures and high pressure may be also mentioned.
The disinfection or sterilization is performed under severe conditions of very strong oxidizability, and thus parts of an endoscope are problematically corroded. Even a molded article which uses a fluorine-containing elastomer with excellent chemical resistance, conventionally, may cause faults such as cracks and swelling, if it is exposed to the severe conditions for a long time. If it is attempted to avoid faults such as cracks and swelling, problems such as occurrence of outgas are raised, and elasticity which is specific to an elastomer may be sometimes impaired. Such an elastomer cannot be used for the endoscope.
For example, JP-A 2005-245517 (KOKAI) proposes molded articles for enhancing resistances under a severe disinfection or sterilization environment. In this publication, two or more kinds of cross-linkable fluorine-containing elastomers are used, and carbon is mixed therewith as a filler. Further, JP-A 2007-211233 (KOKAI) proposes that when a fluorine-containing elastic copolymer is cross-linked, alumina is mixed therewith as a reinforcing agent.
As an outer cover for a curved tube in an endoscope is very thin, if the outer cover is cut or pin holes are formed therein, the endoscope fails due to water leakage. It is required, accordingly, to have physical resistances in addition to the chemical resistance described above for the outer cover for the curved tube in the endoscope. It is desired that the physical resistances are maintained even after the severe disinfection or sterilization is performed. An outer cover for the curved tube in the endoscope having all of the conditions described above has not been obtained yet.